Process and apparatus for obtaining dense carbon dioxide snow directly from liquid carbon dioxide



Aug. 11, 1931. RUFENER ETAL 1,818,816

PROCESS AND APPARATUS FOR OBTAINING DENSE OABBON DIOXIDE sNOw DIRECTLYFROM LIQUID OARBON DIOXIDE Filed Dec. 18, 1928 III [NY eN-roIeS PatentedAug. 11, 1931 UNITED STATES PATENT OFFICE HANS RUFENER AND THEOPHILEICI-IMANN, OF BERN-LIEBEFELD, SWITZERLAND,

ASSIGNOBS, BY MESNE ASSIGNMENTS, TO INTERNATIONAL CARBONIC ENGINEER- INGCOMPANY, OF KENNETT SQUARE, PENNSYLVANIA, A CORPORATION OF DEL- AWAREPROCESS AND APPARATUS FOR OBTAINING DENSE CARBON DIOXIDE SNOW DIRECTLYFROM LIQUID CARBON DIOXIDE Application filed December 18, 1928, Se

This invention relates to a process and apparatus for obtaining dense,spec fically heavy carbon dioxide snow or me directly from liquid carbondioxide.

It is well known to make solid carbon dioxide, so-called carbon dioxidesnow, by allowing liquid carbon dioxide to expand to atmosphericpressure, collecting the snow by filtration, and supplying the vaporsthat are formed to the low-pressure cylinder of the compresser to beliquefied again. Normally the escaping gases are simultaneously employedfor pre-cooling the liquid to be expanded. The loose snow is then madeby high pressure very dense, there being about 10% Sublimated andreckoned as lost. In other words the dry and therefore looser snow whichhas previously been obtained from liquid carbon dioxide is condensedmechanically by compression, about 10% of the snow being converted intogas and lost to the yield.

In contradistinction to this known method the present invention enablesexceedingly dense carbon dioxide snow or ice to be made in a simplephysical manner in one single cycle of operations.

The process according to the present invention comprises the step ofexpanding the vliquid carbon dioxide, for the purpose of forming moistsnow, to a pressure which approximately corresponds to the tripple pointof carbon dioxide.

Further, according to the invention, apparatus for carrying intopractice this improved process is characterized in that an expansionnozzle having a diffuser directly attached thereto serves forintroducing the liquid carbon dioxide into the expansion vessel.

Other features of the invention will be described hereinafter andpointed out in the rial No. 326,898, and in Switzerland June 26, 1928.

Figure 2 shows a detail thereof in the form of a nozzle in longitudinalsection on an enlarged scale.

Referring to the drawings, the apparatus comprises a vertical expansionchamber 1 for liquid carbon dioxide which is supplied through a pipe 2to an expansion nozzle 41 inserted into the cover 3 of the vessel. Theexpansion nozzle 4 runs directly into a diffuser 5a. In the expansionnozzle 5 the liquid carbon dioxide is first expanded to a pressure lyingbelow the tripple point (about 565) of carbon dioxide, in order toobtain snow with certainty. The snow and gas are'then compressed by thediffuser to over the tripple point. This pressure lies between 5-6atmos. In this manner a moist snow it obtained. The wet snow ejectedfrom the diffuser is caught by a screen 6, on which the snow graduallygrows into a block. A pipe 9 having a valve or stop cock 8 is connectedto the removable bottom 7 of the expansion vessel 1. A pipe 10 that isconnected below to the stop cock 8 is connected above to the cover 3 ata situation above an upper screen 11, and can be closed at 12 by a stopcook or valve. Branch pipes 13 and 14 lead to the lowpressure andhigh-pressure cylinders, for example of a two-stage compressor (notshown), so that it is possible to regulate the pressure in the vessel 1as desired by closing or opening one or other of the valves 8 and 12, orby correspondingalternate opening thereof, or by s11pplying more or lessliquid from the pipe 2. According to the desired final pressure in theexpansion vessel and according to the intended density of the carbondioxide snow, the gases that are formed or only a part thereof aresucked away through the block of snow. Owing to these gases (so-calledthrottle vapors) diffusing through the moist plastic mass of snow, asolid coherent icy mass is produced having a high pecifie weight up to1.45. Besides the dense product, owing to working with a higher finalpressure the additional advantage is obtained that a compressor ofrelatively small dimensions can be used, and in consequence of the highsuction pressure the requisite work of compression is less than whenexhausting from one at mosphere.

. When a snow block of the desired height is obtained the connectionwith the high-pressure cylinder is exchanged with that of thelow-pressure compressor, the valve in the pipe 2 being closed. Thepressure in the expansion vessel is thereby reduced to atmosphericpressure and in consequence of the fall in temperature to 80 0., themoist mass of snow is caused to congeal. When the bottom 7 of the vessel1 is removed with the filter 6 the icy snow block in the usualcommercial form can be removed below from the vessel 1 that has acorresponding cross-section, and those losses due to radlation which areunavoidable with known processes do not occur. After closing theexpansion vessel the described process can be repeated. The escapinggases can be used during the process for cooling the liquid carbondioxide to be used, in order stlll more to increase the efficiency ofthe process.

By means of the described process dense carbon dioxide snow or. ice isobtained in one single cycle of operations and without the aid of apress.

Various modifications may be made in the details of construction of theapparatus described above within the scope of the invention as definedby the claims.

We claim 1. A process of obtaining dense, specifically heavy carbondioxide ice from liquid carbon dioxide, including the steps of expandingthe liquid carbon dioxide to a pressure that corresponds approximatelyto the triple point of carbon dioxide, whereby snow and gases areproduced, and in compelling gas to diffuse through the snow in order tocompress the snow in a single operation simultaneously with a furtherreduction of pressure to form the snow into a mass of higher density.

2. Apparatus for obtaining dense, specifically heavy carbon dioxide icefrom liquid.

carbon dioxide, comprising in combination, an expansion vessel, anexpansion nozzle for admitting liquid carbon dioxide into said vessel, ascreen in said vessel for receiving snow formed therein, and a pipe thatopens into said vessel at the side of said screen remote from saidnozzle for drawing off from the vessel gas formed therein through thesnow on the screen and through the screen.

3. Apparatus for obtaining dense, specifically heavy carbon dioxide icefrom liquid carbon dioxide, comprising in-combination, an expansionvessel, an expansion nozzle in the upper part thereof for admittingliquid carbon dioxide into the vessel, a screen in the vessel below saidnozzle for collecting snow formed in the vessel, a pipe that opens intosaid vessel at a location above said screen for withdrawing gas thatinto the vessel below the screen and serves to draw off gas from thevessel through the snow on the screen.

4. In a process of forming a dense specifically heavy carbon dioxide icefrom liquid carbon dioxide, those steps which consist in, admittingliquid carbon dioxide into a chamber while maintaining the pressure inthe chamber corresponding approximately to the triple point of carbondioxide with resulting formation of a mass of carbon dioxide snow in thechamber, and finally reducing the pressure on and removing such mass ofsnow from the chamber.

5. In a process of forming a dense specifically heavy carbon dioxide icefrom liquid carbon dioxide, those steps which consist in, admittingliquid carbon dioxide into a chamber while maintaining the pressure inthe, chamber approximately corresponding to the triple point of carbondioxide with resulting formation of a mass of moist carbon dioxide snowtherein, and then solidifying and hardening the moist snow mass.

6. In a process of forming a dense, specifically heavy carbon dioxideice; expanding liquid carbon dioxide to a pressure approxi matelycorresponding to the triple point of carbon dioxide with the resultingformation of a mass of moist carbon dioxide snow therefrom, maintainingthe mass of snow during formation thereof at a pressure approximatelycorresponding to the triple point pressure, and solidifying the mass ofmoist snow into a block of carbon dioxide ice.

7. A process of forming a dense, specifically heavy carbon dioxide icefrom liquid carbon dioxide, comprising the steps of; expanding liquidcarbon dioxide to a pressure corresponding approximately to the triplepoint of carbon dioxide, with the resulting formation of a moist carbondiox-' ide snow, collecting the moist snow while maintaining the sameunder approximately the aforesaid pressure; and finally subjecting thecollected mass of moist snow to a decrease in pressure down toapproximately atmospheric pressure to congeal and solidify the same intoa dense, specifically heavy mass of carbon dioxide ice.

8. A process of forming dense, specifically heavy carbon dioxide icefrom liquid carbon dlOXldG, consisting in the stepsof; expanding liquidcarbon dioxide in a chamber to a pressure corresponding approximately tothe triple point of carbon dioxide to form a wet carbon dioxide snow andcarbon dioxide gas in the chamber, collecting the wet snow so formed inthe chamber while maintaining the chamber pressure at approximately thetriple point of carbon dioxide, and then drawing off and diffusingcarbon dioxide gas in the chamber through the collected wet snow whilereducing the chamber pressure to congeal and solidify the Wet snow intoa block of carbon dioxide ice.

9. A process of forming a dense specifically heavy carbon dioxide ice,consisting in the steps of; expanding liquid carbon dioxide in a chamberto a pressure corresponding approximately to the triple point of carbondioxide with the production of a wet carbon dioxide snow and gases,collecting the wet snow in the chamber while drawing off the gases fromand maintaining the pressure in the chamber at approximately the triplepoint of carbon dioxide, and then reducing the pressure in the chamberto congeal and solidify the collected mass of wet snow therein into a,block of dense, specifically heavy carbon dioxide ice.

10. A process of forming dense, specifically heavy carbon dioxide ice,including the steps of; expanding liquid carbon dioxide to a pressure atwhich a wet carbon dioxide snow is produced, collecting said wet snowwhile maintaining a wet snow preserving pressure thereon, and finallysubjecting the wet snow to a further decrease in pressure with resultinglowering of the temperature to congeal and solidify the snow into acoherent block of dense, specifically heavy carbon dioxide ice.

11. A process of producing a dense, specifically heavy carbon ,dioxideice, consisting in discharging and expanding liquid carbon dioxide intoa chamber in which the pressure corresponds approximately to the triplepoint of carbon dioxide with resulting expansion of the liquid andformation thereof into a wet carbon doxide snow and gases, withdrawingthe gases from the chamber while maintaining a wet snow preservingpressure therein and permitting the wet snow to collect in the chamber,then stopping discharge of liquid into the chamber, and finally reducingthe chamber pressure to congeal and solidify the wet snow into a mass ofcarbon dioxide ice of higher density and specific weight.

12. A process of obtaining a dense, specifically heavy carbon dioxideice from liquid carbon dioxide, including the steps of; discharging andexpanding liquid carbon dioxide into a chamber to a pressurecorresponding approximately to the triple point of carbon dioxide withresulting formation of wet carbon dioxide snow and vapors therefrom,withdrawing the vapors from the chamber during snow forming dischargeand expansion of liquid therein while regulating the pressure in thechamber to maintain wet snow preserving conditions therein, stoppingwithdrawal of vapors and cutting off discharge of liquid into thechamber, and then diffusing vapors through the collected snow andwithdrawing such vapors from the chamber while simultaneously reducingthe pressure in the chamber to con eal and solidify the snow into a massof car on dioxide ice of higher density and specific weight.

13. A process of producing dense, specifically heavy carbon dioxide icefrom liquid carbon dioxide, including the steps of; expanding liquidcarbon dioxide into a chamber to a pressure corresponding approximatelyto the triple point of carbon dioxide with resulting formation of a wetcarbon dioxide snow and vapors in the chamber, withdrawing vapors fromthe chamber during expansion of'liquid thereinto to regulate andmaintain a wet snow preserving .pressure in the chamber while formingand collecting a mass of wet snow therein, stopping withdrawal of vaporsfrom the chamber to regulate the final pressure on the wet snow masstherein, then cutting off discharge of liquid to the chamber, andfinally reducing the chamber pressure to congeal and solidify the snowinto a mass of carbon dioxide ice of higher density and specific weight.1

14. A rocess of producing a cake or block of ense, specifically heavycarbon dioxide ice, comprisingthe steps of; forming and collecting amass of wet carbon dioxide snow in a chamber while maintaining thechamber pressure corresponding approximately to the triple point ofcarbon dioxide, and finally reducing the chamberpressure toapproximately atmospheric pressure with corresponding drop intemperature and congelation and solidification of the snow mass into ablock or cake of dense, specifically heavy carbon dioxide ice'forremoval from the chamber for use.

15. A process of producing dense, specifically heavy carbondioxide icefrom liquid carbon dioxide, consisting in the steps of; ex-

panding liquid carbon dioxide into a chamducing the chamber pressurewith resulting solidification of the snow mass into a block of dense,specifically heavy carbon dioxide me.

16. Apparatus for obtaining dense, specifically heavy carbon dioxide icefrom liquid carbon dioxide, comprising in combination,

an expansion vessel, an expansion nozzle for admitting liquid carbondloxlde mto said vessel to form carbon dioxide snow and vapors therein,a member in said vessel below said nozzle providing-a surface forreceiving and on which the snow collects, and said vessel provided witha vapor outlet below said nozzle, and below the level of snow to becollected on said member, for drawing olf vapor from the chamber anddiffusing the vapor through the collected snow.

In testimony whereof we affix our signatures.

HANS RUFENER. THEOPHIL EICHMANN.

